•Electrochemical oxidizing carbon cloth (CC) followed by mild acidification realizes uniformly anchoring amorphous molybdenum sulfide on CC (MoSx/CC).•Excessive oxidation will lead to the lack of ...highly active defect MoV sites in the quantity and nature for the as-synthesized MoSx/CC samples.•The optimal MoSx/CC samples exhibit excellent activity in hydrogen evolution reaction (HER) due to boosting highly active defect MoV sites.•This work presents a novel strategy for enhancing the HER activity of MoSx-based materials from the catalyst-substrate effect.
Simultaneously achieving abundant active sites and high intrinsic activity is a major challenge to developing highly efficient MoSx-based materials for hydrogen evolution reaction (HER) since there might be a contradictory relationship between loading amounts and intrinsic activity of amorphous molybdenum sulfide (MoSx). Herein, we have for the first time demonstrated a strategy for the electrochemical oxidation of carbon cloth (CC) followed by mild acidification employing (NH4)2MoS4 as the precursor to boost highly active defect MoV sites (DMSs) for MoSx toward efficient HER. In our strategy, a high potential at the anode results in a high concentration of O-containing groups on the surface of CC, which favors loading Mo3S132− clusters or MoSx on CC (MoSx/CC) for achieving abundant DMSs. Impressively, such oxidation does not disrupt the sp2 hybridized carbon of the substrate. Hence, the excellent conductivity of CC guarantees high intrinsic activity of the as-synthesized MoSx/CC samples. On the other hand, excessively high potential stimulates excessive growth and accumulation of Mo3S132− clusters for further increasing loading amounts of MoSx. Nevertheless, such loading is at the expense of DMSs, indicating a great decrease in the quantity of active sites. Furthermore, excessive oxidation leads to unsatisfactory conductivity of CC, owing to breaking the sp2-conjugated system of CC. At the same time, the theoretical prediction and experimental investigation reveal that the intrinsic activity of DMSs will significantly decrease at excessively high potential. By regulating electrochemical potential to 1.8 V, a balance between the loading amounts of MoSx and intrinsic activity of MoSx/CC is achieved to boost highly active DMSs for efficient HER. Consequently, the optimal MoSx/CC exhibit the most excellent HER activity among all counterparts, accompanied by reliable stability. This work presents a new strategy for realizing abundant active sites with high intrinsic activity for MoSx-based materials toward efficient HER from the catalyst-substrate effect.
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Semantic Feature Modeling Based on Geometric Constraint Solving Gao, Xue Yao; Zhang, Chun Xiang; Yu, Xiao Yang
Applied Mechanics and Materials,
02/2014, Volume:
513-517, Issue:
Applied Science, Materials Science and Information Technologies in Industry
Journal Article
Peer reviewed
Semantic feature modeling is a new trend of CAD technology. It is very important for modifying and editing models automatically and semi-automatically. In this paper, a semantic feature modeling ...method is proposed, in which geometric constraints of models are solved. The new method is history-independent. At the same time, the architecture of semantic feature modeling is given. According to the principles of 3 dimensional rigid bodies, basic geometric constraints can be expressed. Experiment results show an instance modeled by the proposed method.
New and ordered 2D-hexagonal (
p6
mm) mesoporous aluminosilicates (CMI-11) have been synthesized in strongly alkaline media using aluminosilicate ester ((Bu
s
O)
2-Al-O-Si-(OEt)
3) as single-source ...molecular precursor and CTMABr as surfactant and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N
2 adsorption–desorption and
27Al and
29Si MAS NMR spectroscopy. These mesoproous aluminosilicates exhibit a very low Si/Al ratio of 1.9 and highly thermal stable tetrahedral aluminum sites in the mesoporous walls.
27Al and
29Si MAS NMR spectroscopy indicates that the pore walls of CMI-11 are fully condensed with molecular homogeneity of Si–O–Al linkage. These materials are highly important in catalysis, in particular for the petroleum processing and the bulky molecules treatment.
Two supramolecular architectures based on polyoxometalates: 4,4′-Hbpy
2Ni(4,4′-bpy)
2(H
2O)
4AsW
VI
11W
VO
40·4H
2O (
1) and 4,4′-H
2bpy
2PMo
VI
9Mo
V
3O
40·2H
3O (
2) (4,4′-bpy
=
4,4′-bipyridine) ...have been prepared under hydrothermal conditions and characterized by elemental analyses, IR spectra, XPS spectra and single crystal X-ray diffraction analyses. The two compounds consist of 4,4′-bpy units with different polyoxometalates,
α-Keggin AsW
VI
11W
VO
40
4− and pseudo-Keggin PMo
VI
9Mo
V
3O
40
6−, respectively. No direct interactions occur among polyoxoanions in these two compounds, but the clusters together with metal-organic units or organic 4,4′-bpy units and/or water molecules construct the high-dimensional supramolecular networks through hydrogen bonds. The crystal structure analyses reveal that the organic 4,4′-bpy units have a major influence on the packing arrangements of crystals.
The composition scheme of speed target value of railway engineering contains the functional orientation of railway line,demand of time target value and the adaptation to the adjacent lines. The ...selected speed target value of railway engineering must be suited to the features of the railway, satisfied with transport requirement, accorded to railway developing strategy and realized to the best economic benefit.This paper comprehensively compares and analyzes different speed target value schemes adopted by Revamping project for Capacity expansion of WANGAN railway and a reasonable speed target value—200km/h reserved 250 km/h is recommended.
Abstract
Background and study aims
Biopsies of non-specific mucosal findings are often performed during esophagogastroduodenoscopy (EGD). We sought to determine the prevalence and clinical utility ...of non-targeted biopsies of the stomach and esophagus.
Patients and methods
We conducted a retrospective review of 949 outpatient EGDs performed at a US tertiary referral center. Non-targeted biopsies of the stomach were defined as either “normal” or “mild” to “moderate” “erythema” or “inflammation” without other endoscopic features. Non-targeted biopsies of the esophagus and gastroesophageal junction (GEJ) were defined as endoscopically “normal” mucosa. The primary outcome was the proportion of non-targeted biopsies resulting in “definite management change.” Secondary outcomes included histopathologic diagnoses of Helicobacter pylori, intestinal metaplasia and esophageal eosinophilia.
Results
Of 949 EGDs, 332 (35.0 %, 95 % CI 31.9 – 38.1 %) had a non-targeted biopsy taken at any site. Erythema in the gastric body and antrum was biopsied at a rate of 83 – 86 %, while biopsies of “normal”-appearing mucosa occurred at rates from 3 % (GEJ) to 15 % (body and antrum). The percentage of non-targeted biopsies that led to definite management change ranged from 5 % in the GEJ and esophagus to 9 % in the antrum, but did not significantly differ by mucosal appearance. Multivariable regression analyses suggested associations of language and age > 50 with management change from non-targeted gastric biopsy.
Conclusions
Non-targeted biopsies of the stomach and esophagus led to definite management change in a small proportion of patients. Further studies are needed to identify patient and/or endoscopic characteristics and techniques to improve the yield of this practice.
Very uniform and well shaped Mn3O4 nano‐octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape‐directing agent. The ...nano‐octahedra formation mechanism is monitored. The shape and crystal orientation of the nanoparticles is reconstructed by scanning electron microscopy and electron tomography, which reveals that the nano‐octahedra only selectively expose {101} facets at the external surfaces. The magnetic testing demonstrates that the Mn3O4 nano‐octahedra exhibit anomalous magnetic properties: the Mn3O4 nano‐octahedra around 150 nm show a similar Curie temperature and blocking temperature to Mn3O4 nanoparticles with 10 nm size because of the vertical axis of 001 plane and the exposed {101} facets. With these Mn3O4 nano‐octahedra as a catalyst, the photodecomposition of rhodamine B is evaluated and it is found that the photodecomposition activity of Mn3O4 nano‐octahedra is much superior to that of commercial Mn3O4 powders. The anomalous magnetic properties and high superior photodecomposition activity of well shaped Mn3O4 nano‐octahedra should be related to the special shape of the nanoparticles and the abundantly exposed {101} facets at the external surfaces. Therefore, the shape preference can largely broaden the application of the Mn3O4 nano‐octahedra.
Uniform and well shaped Mn3O4 nano‐octahedra synthesized with PEG200 using a simple hydrothermal method exhibit anomalous magnetic properties in regard to their Curie and blocking temperatures. These Mn3O4 nano‐octahedra also show high performance in the photodecomposition of organic pollutants. The anomalous magnetic properties and superior photodecomposition activity of the Mn3O4 are thought to be related to their special shape: the vertical axis of the 001 plane and the abundantly exposed {101} facets at the surfaces. They are promising magnetic materials and as starting materials in the preparation of soft magnetic materials such as manganese ferrite for dioxymagnetic cores in transformers for power supplies, in the lithiation of Li‐Mn‐O electrode materials for rechargeable lithium batteries, and in a corrosion‐inhibiting pigment for epoxy‐polyamide‐ and epoxy‐ester‐based primers and top coatings. For more information, please read the Full Paper “Well Shaped Mn3O4 Nano‐octahedra with Anomalous Magnetic Behavior and Enhanced Photodecomposition Properties” by B.‐L. Su and co‐workers, beginning on page 474.
Bone marrow mesenchymal stem cell (BMSC) is a potentially effective vehicle for the cell and gene therapy in clinical disease treatment. We studied whether the most commonly used anesthetic drugs ...have negative effects on rat BMSCs in vitro.
The cultured BMSCs were treated with sevoflurane (in 1.7%, 2.3%, and 3%); propofol (5 μg/ml, 10 μg/ml and 20 μg/ml); or 2.3% sevoflurane plus 10 μg/ml propofol. After 4-hour treatment, the cultured BMSCs were prepared for MTT reduction assays and cell morphology observation.
Compared to the controls, the 4-hour sevoflurane exposure resulted in decreased cell viability of BMSCs in a concentration-dependent manner; however, 1.7% sevoflurane did not reduce the cell viability. The 4-hour propofol treatment did not affect the cell viability; but combined usage of 2.3% sevoflurane and 10 μg/ml propofol decreased cell viability. In BMSCs treated with higher concentration of sevoflurane (1.7% and 2.3%) and combined usage of the two anesthetics, the cell became raritas with wizened cytoplasm and had fewer connections to each other of BMSCs. More than 2.3%, or 2.3% sevoflurane plus 10 μg/ ml propofol caused cytotoxicity to BMSCs. However, propofol up to 20 μg/ml did not harm the BMSCs.
The study indicates that it is necessary to choose the right anesthesia during the BMSCs transplantation therapy.
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